Magnetoresistance of a 2D electron gas caused by electron interactions in the transition from the diffusive to the ballistic regime

On a high-mobility 2D electron gas we have observed, in strong magnetic fields (omega(c)tau>1), a parabolic negative magnetoresistance caused by electron-electron interactions in the regime of k(B)Ttau/hsimilar to1, which is the transition from the diffusive to the ballistic regime. From the temperature dependence of this magnetoresistance the interaction correction to the conductivity deltasigma(xx)(ee)(T) is obtained in the situation of a long-range fluctuation potential and strong magnetic field. The results are compared with predictions of the new theory of interaction-induced magnetoresistance.